Doctors who allowed a young woman to kill herself acted within the law, a coroner has ruled.

Kerrie Wooltorton is believed to be the first person to have used a living will to kill herself. She was admitted to hospital after poisoning herself but doctors said they had no alternative but to allow her to die.

The 26-year-old had written the will on 15 September 2007, three days before she drank poison and phoned an ambulance, the inquest heard this week. She was taken to Norfolk and Norwich University hospital, where she presented staff with the document.

The will said that if she called for an ambulance it was not because she wanted life-saving treatment but because she did not want to die in her flat alone or in pain. Wooltorton died the next day in hospital.

The inquest heard that she had depression when she died. She drank poison up to nine times in the 12 months before her death, but each time doctors intervened to save her.

Dr Alexander Heaton, the hospital's consultant renal physician, said he had "no alternative" but to follow Wooltorton's will.

"I would have been breaking the law and I wasn't worried about her suing me, but I think she would have asked, 'What do I have to do to tell you what my wishes are?'" he said. "It's a horrible thing to have to do but I felt I had no alternative but to go with her wishes. Nobody wants to let a young lady die."

The coroner, William Armstrong, recorded a narrative verdict that does not blame the hospital for Wooltorton's death at the Assembly House in Norwich on Monday.

He said: "She had capacity to consent to treatment which, it is more likely than not, would have prevented her death. She refused such treatment in full knowledge of the consequences and died as a result."

Living wills, or advance decisions, were introduced under the Mental Capacity Act 2005 but are more commonly associated with terminally ill patients who want to refuse treatment. The government's Directgov website says a valid advance decision means "treatment cannot lawfully be given – if it were, the doctor might face civil liability or criminal prosecution".

The ProLife Alliance today called for the law on living wills to be changed and said doctors had warned before the 2005 act was introduced that the legislation could put them in an "impossible situation".

"Doctors treating attempted suicides say that the overwhelming majority are glad to have been saved," said the ProLife chairman, Dominica Roberts. "A doctor should never act as if any person's life is worthless."

But Dignity in Dying said although the situation had been difficult for health professionals this should not detract from a patient's wishes. "It is important that advance decisions are respected," said Jo Cartwright, a spokeswoman. "But this is reliant on the person whose advance decision is being acted upon having the capacity to make the decision when it was made."

Andrew Stronach, spokesman for Norwich and Norfolk University hospitals, said the law was clear that a mentally competent patient had the right to refuse treatment.

"The challenge for staff was to determine whether or not she was mentally competent, which she was," Stronach said. "The doctors involved took second opinions, sought the advice of the medical director, and did everything that they should have done."